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Placement accuracy and primary stability of implants in the esthetic zone using dynamic and static computer-assisted navigation: A retrospective case-control study
Research Assistant, Hospital of Stomatology, Guanghua School of Stomatology, Guangdong Provincial Key Laboratory of Stomatology, Sun Yat-sen University, Guangzhou, PR China
Research Assistant, Hospital of Stomatology, Guanghua School of Stomatology, Guangdong Provincial Key Laboratory of Stomatology, Sun Yat-sen University, Guangzhou, PR China
Research Assistant, Hospital of Stomatology, Guanghua School of Stomatology, Guangdong Provincial Key Laboratory of Stomatology, Sun Yat-sen University, Guangzhou, PR China
Research Assistant, Hospital of Stomatology, Guanghua School of Stomatology, Guangdong Provincial Key Laboratory of Stomatology, Sun Yat-sen University, Guangzhou, PR China
Graduate student, Hospital of Stomatology, Guanghua School of Stomatology, Guangdong Provincial Key Laboratory of Stomatology, Sun Yat-sen University, Guangzhou, PR China
Research Assistant, Hospital of Stomatology, Guanghua School of Stomatology, Guangdong Provincial Key Laboratory of Stomatology, Sun Yat-sen University, Guangzhou, PR China
Professor, Hospital of Stomatology, Guanghua School of Stomatology, Guangdong Provincial Key Laboratory of Stomatology, Sun Yat-sen University, Guangzhou, PR China
Corresponding author: Dr Zhuofan Chen, Hospital of Stomatology, Guanghua School of Stomatology, Guangdong Provincial Key Laboratory of Stomatology, Sun Yat-sen University, No. 56 Lingyuan Rd West, Guangzhou 510055, PR CHINA
Professor, Hospital of Stomatology, Guanghua School of Stomatology, Guangdong Provincial Key Laboratory of Stomatology, Sun Yat-sen University, Guangzhou, PR China
Both the placement accuracy and primary stability of implants are important to implant therapy in the esthetic zone. The effect of dynamic and static computer-assisted navigation on the primary stability of implants in the esthetic zone remains uncertain.
Purpose
The purpose of this case-control study was to investigate the effect of dynamic and static computer-assisted navigation on the placement accuracy and primary stability of implants in the esthetic zone.
Material and methods
Partially edentulous participants who received at least 1 implant in the anterior maxilla using either fully guided static or dynamic computer-assisted implant surgery (s-CAIS, d-CAIS) from January 2020 to February 2022 were screened. Participant demographic information, timing of implant placement, primary stability represented by the insertion torque value (ITV) in Ncm, and implant survival were collected from the treatment record. Bone quality at the implant sites was determined according to the Lekholm and Zarb classification. The accuracy of implant placement represented by the linear (platform: Dpl, mm; apex: Dap, mm) and angular deviations (axis: Dan, degree) between the planned and placed implants was evaluated based on the preoperative surgical plan and postoperative cone beam computed tomography (CBCT) data. A statistical analysis of the data was completed by using the chi-square, Fisher exact, Student t, and Mann-Whitney U tests (α=.05).
Results
A total of 32 study participants (38 implants) were included. The groups of s-CAIS (16 participants, 18 implants) and d-CAIS (16 participants, 20 implants) were statistically comparable in sex (P=.072), age (P=.548), bone quality (P=.671), and timing of implant placement (P=.719). All implants survived during an average follow-up period of 13 months. The d-CAIS group showed close linear deviations (Dpl 1.07 ±0.57 mm, Dap 1.26 ±0.53 mm) but lower angular deviation (Dan 2.14 ±1.20 degrees) and primary stability (ITV 25.25 ±7.52 Ncm) than the s-CAIS group (Dpl 0.92 ±0.46 mm, Dap 1.31 ±0.43 mm, Dan 3.31 ±1.61 degrees, ITV 30.56 ±11.23 Ncm, PDpl=.613, PDap=.743, PDan=.016, PITV=.028).
Conclusions
Comparable linear positioning accuracy and higher angular deviation were found for implants placed in the esthetic zone by using s-CAIS than when using d-CAIS. Higher primary stability of implants may be achieved by using s-CAIS, as s-CAIS seemed to have higher osteotomy accuracy than d-CAIS.
Clinical Implications
With a clinically comparable placement accuracy, both s-CAIS and d-CAIS could be used to obtain the optimal 3D position of implants placed in the esthetic zone. However, s-CAIS may be a better option for the immediate and early implant placement in the esthetic zone because of its higher osteotomy accuracy in preparing the implant bed.
Implant-supported prostheses have been widely used for partially and completely edentulous patients. However, implant placement in the esthetic zone remains a challenge and has been classified as “advanced” or “complex” according to the straightforward, advanced, complex (SAC) classification.
While most patients with a missing tooth in the esthetic zone have multiple esthetic risk factors and high expectations, the preexisting anatomy in the anterior maxilla makes it difficult to obtain the optimal 3-dimensional (3D) position of implants, which plays a crucial role in the long-term stability of peri-implant hard and soft tissue.
Many complications associated with the placement of dental implants, such as poor esthetics, interproximal bone loss, and even peri-implantitis, can be attributed to inaccurate positioning.
Static computer-assisted implant surgery (s-CAIS) has been recommended to correctly place implants in the esthetic zone, with advantages that include higher accuracy and less invasion and morbidity than the free-hand approach.
However, s-CAIS has disadvantages, including the time-consuming preoperative preparation, the cost of designing and fabricating surgical guides, and the limited cooling irrigation for the implant bed.
Differing from s-CAIS by transferring the virtual surgical design with prefabricated templates, d-CAIS guides dental surgeons by tracking and superimposing the position of surgical instruments and jaws on the preoperative 3D images and provides real-time feedback intraoperatively.
Comparison of the accuracy of implant position for two-implants supported fixed dental prosthesis using static and dynamic computer-assisted implant surgery: a randomized controlled clinical trial.
Expectation and reality of guided implant surgery protocol using computer-assisted static and dynamic navigation system at present scenario: evidence-based literature review.
d-CAIS appears to be safer, more flexible, and more accurate than s-CAIS. In addition, the effect of d-CAIS on the accuracy of implant placement has not been fully investigated in the esthetic zone.
The sample size of implants placed in the esthetic zone using d-CAIS in previous studies was either unreported or rather small (only 4 in 1 study and 11 in another).
Additionally, while the accuracy of implant placement has been extensively discussed, little attention has been paid to the effect of CAIS on osteotomy accuracy, which may affect the primary stability of implants.
Accuracy and primary stability of tapered or straight implants placed into fresh extraction socket using dynamic navigation: a randomized controlled clinical trial.
As an influencing factor of osteointegration, primary stability appears to be more important to clinical decision-making for the timing of restoration and loading, especially for implants in the esthetic zone where immediate restoration and loading are expected by patients.
In the conventional preparation of the implant bed (without bone condensing or underpreparation), the primary stability of an implant inserted in a certain site would be largely determined by the accuracy of the osteotomy with the surgical technique used.
A low osteotomy accuracy may lead to excessive bone removal, an overprepared implant bed, and poor primary stability, even though the accuracy of implant placement is high.
The current study aimed to investigate the effect of d-CAIS on the accuracy of osteotomy and implant placement when used in the esthetic zone. The 3D position deviations and the primary stability of implants placed by using d-CAIS were evaluated and compared with those of implants placed by using s-CAIS. The null hypothesis was that no difference would be found in the placement accuracy and primary stability of implants placed by using d-CAIS and s-CAIS.
Material and methods
This retrospective case-control study was approved by the university’s ethics committee (KQEC-2022-11-01) and was registered in the Chinese Clinical Trial Registry (ChiCTR2200058077). Informed consent had been obtained before the implant surgery. The study was conducted according to the principles stated in the Helsinki Declaration. All study participants had received an implant surgery in the university dental clinic between January 2020 and February 2022. Only partially edentulous patients who had received at least 1 implant in the anterior maxilla by using fully guided s-CAIS (Fig. 1) or d-CAIS (DHC DI2; Dcarer) (Fig. 2) were eligible for inclusion in the study. Demographic information (name, sex, age) and detailed treatment records that included the surgical plan, the timing of implant placement, the insertion torque value (ITV) in Ncm, and the implant information (brand and size) were collected.
Figure 1Treatment process of s-CAIS. A, Preoperative planning. B, Intraoral setting of surgical guide. C, Fully guided implant placement. D, Bone augmentation. E, Immediate restoration with interim prosthesis. s-CAIS, static computer-assisted implant surgery.
Figure 2Treatment process of d-CAIS. A, Preoperative planning. B, Calibration of surgical instruments. C, Registration of participant jaws. D, Implant bed preparation. E, Implant placement. F, Three-dimensional guidance and real-time feedback on screen of d-CAIS system. d-CAIS, dynamic computer-assisted implant surgery; 3D, 3-dimensional.
Inclusion criteria were partially edentulous anterior-maxilla fully guided implant placement by using s-CAIS or d-CAIS and accessible treatment records, including the preoperatively designed surgical plan, the operation records, and the postoperative CBCT images (Fig. 3A). Exclusion criteria were partially or completely edentulous maxilla where the tooth-supported surgical guides could not be firmly seated, the surgical plan was modified intraoperatively or postoperatively, the s-CAIS surgical plans were unreadable with the software program (coDiagnostiX, v.9.17.0.379; Dental Wings Inc), and the implant position was not identifiable in the postoperative CBCT images (Fig. 3B).
Figure 3Representative postoperative CBCT images. A, Useable images with implant distinguishable from surrounding tissue. B, Unusable images with implant indistinguishable from surrounding tissue. CBCT, cone beam computed tomography.
on the linear and angular deviations between the planned and placed implants by using s-CAIS and d-CAIS. The minimum required sample size for the platform, apex, and angular deviations was separately calculated as 7, 4, and 12 with a software program (G∗power, v.3.1.9.7; Heinrich-Heine-University Düsseldorf) for 2 independent means comparison (t test) with 90% study power and a significance level of .05 (α=.05, 2 tails).
The evaluation of the placement accuracy of the virtually planned and actually placed implants was carried out by an individual (Huang R.X.) who was blinded to the study design. The intraexaminer reliability (interclass coefficient=0.980, P=.001) was calculated by evaluating the same data set of 5 participants twice at 2 different time points. The placement accuracy was represented by the linear deviations at the apex (Dap, mm) and the central point of the platform (Dpl, mm), as well as the angular deviation (Dan, degree) between the planned and placed implants (Fig. 4). Specifically, for the s-CAIS group, the postoperative CBCT images were imposed onto the preoperative 3D images with the virtually designed implants by matching the anatomic structures with coDiagnostiX. In detail, some anatomic structures were manually selected, and digital calculation and matching by the software program followed. Then, the platform and apex of the placed implants were determined manually. Finally, the deviations were calculated automatically by the software program. For the d-CAIS group, the accuracy evaluation was carried out with a software program (Accuracy Analysis of Dcarer Dynamic Implant Navigation, v.1.0; Dcarer). The steps were the same as those of the s-CAIS group, except for an additional algorithm registration following the first registration based on the matching of anatomic structures.
Figure 4Evaluation of implant placement accuracy. Light gray: virtually planned implant. Dark gray: actually placed implant. Dan, angular deviation between implant axes; Dap, 3D deviation at apical point; Dpl, 3D deviation at central point of platform.
The timing of implant placement was determined based on the treatment records, including immediate implant placement, early implant placement with soft-tissue healing (4-8 weeks of healing), early implant placement with partial bone healing (12-16 weeks of healing), and late implant placement (more than 6 months of healing).
The bone quality at each implant site was represented by bone type. Specifically, the preoperative CBCT sagittal image on the middle line of the coronal view was selected for the determination of bone type according to the Lekholm and Zarb classification.
For an extraction socket planned for immediate implant placement, the apicopalatal region where the future implant would be placed was evaluated. Two examiners (L.Y.X., L.R.H.) were involved in the first evaluation, with disagreements resolved by a third examiner (L.Q.). Interexaminer reliability (interclass coefficient=0.900, P=.003) was calculated based on the evaluation of the same data set (n=5).
The ITV in Ncm was used to represent the primary stability of implants as it was readily obtainable from the treatment record.
The ITV was routinely checked with a torque wrench (ratchet and torque control device; Institut Straumann A/S) when the implants were placed to determine the timing of restoration and loading.
Study participants were enrolled after applying the inclusion and exclusion criteria. Selection and information biases were minimized by the specific treatment record of the study participants.
A statistical analysis was carried out with a software program (IBM SPSS Statistics, v25; IBM Corp). Data distribution was checked with the Shapiro-Wilk test. The chi-square or Fisher exact test was adopted to compare the sex of study participants, the bone quality, and the timing of implant placement. The Student t test was used for the comparisons in age, ITV, Dap, Dpl, and Dan when the distribution was normal. Otherwise, the nonparametric test (Mann-Whitney U test) was used (α=.05). As the evaluated sample size was small, a power estimate was carried out for any index with P<.05 (1 tail) by using the Compromise Power Analysis in G∗Power.
Of the 741 patients (1087 implants) whose records were evaluated, only 16 participants (20 implants) treated with d-CAIS and 16 participants (18 implants) with s-CAIS were included in this study (Fig. 5). No statistical difference was found in the sex and age of the 2 groups (Table 1). The implants were bone-level-tapered, with the same diameter of 3.3 mm and a length in the range of 10 to 14 mm (BLT; Institut Straumann A/S) (Table 2). All included implants in the 2 groups survived during the 13 ±6-month follow-up period and supported ceramic single crowns which were either screw retained or cement retained with custom titanium-zirconia abutments.
Most of the implants were placed in unhealed alveolar sockets (immediate and early placement with soft-tissue healing). Only 4 implants in the s-CAIS group and 6 in the d-CAIS group were inserted in the healed sockets. No implants were recorded for the early placement with partial bone healing. The timing of implant placement was not significantly different between the 2 groups (P=.719) (Table 3). The bone quality at the implant sites was mainly of type III and IV. The distribution of these bone types was statistically comparable between groups s-CAIS and d-CAIS (P=.671) (Table 4).
Counts for immediate and early implant placement merged for analysis since expected counts for 3 cells (ǂ) were less than 5 and both had unhealed alveolar sockets.
No implant for early placement with partial bone healing (12-16 weeks).
As shown in Table 5 and Figure 6, the ITV of the s-CAIS group was statistically higher than that of the d-CAIS group (P=.028). Dpl and Dap were not statistically different between the 2 groups (PDpl=.613, PDap=.743). The Dan of the s-CAIS group was slightly higher than that of the d-CAIS group (P=.016). As calculated by G∗Power, the level of power for ITV and Dan was greater than 0.8.
Table 5Comparisons between implants placed with s-CAIS and d-CAIS
The null hypothesis of the present study was rejected because differences were observed in the placement accuracy and primary stability of the implants placed by using s-CAIS and d-CAIS.
The placement accuracy of implants in the s-CAIS and d-CAIS groups was comparable with that reported in clinical studies.
Comparison of the accuracy of implant position for two-implants supported fixed dental prosthesis using static and dynamic computer-assisted implant surgery: a randomized controlled clinical trial.
This might be attributed to the difference between the implant sites, as the Dan of d-CAIS from the anterior maxilla was much closer to that of the present study.
Accuracy and primary stability of tapered or straight implants placed into fresh extraction socket using dynamic navigation: a randomized controlled clinical trial.
which is possible because of the influence of clinical factors such as the diversity of anatomic structures and participant cooperation during surgery.
Comparison of the accuracy of implant position for two-implants supported fixed dental prosthesis using static and dynamic computer-assisted implant surgery: a randomized controlled clinical trial.
This might be attributed to the real-time feedback and intraoperative adjustment of d-CAIS. In contrast, intraoperative adjustment is not possible with s-CAIS because of the restriction of the surgical guide.
However, such a small difference (1.5 degrees) should have little clinical significance. Thus, the accuracy of implant placement in the d-CAIS group was considered to be as high as that in the s-CAIS group.
Primary stability can be affected by implant characteristics, bone quantity and quality, and surgical techniques.
Thus, the implant and bone characteristics should be considered when investigating the effect of d-CAIS on primary stability. In the present study, the included implants were a bone-level-tapered design with the same diameter. In spite of the different length, such implants had the same tapered apex (5 mm long) that made a major contribution to primary stability by self-tapping into the cancellous bone.
Immediate implant placement with transmucosal healing in areas of aesthetic priority. A multicentre randomized-controlled clinical trial I. Surgical outcomes.
As shown in Table 3, the majority of implants were placed in extraction sockets without bone healing, indicating that the primary stability of such implants mainly relied on the anchor between the tapered apex and the apicopalatal cancellous bone of the sockets. Additionally, the anterior maxilla was mainly a type III bone,
corresponding to the finding of the present study (Tables 4 and 5). Therefore, the implant characteristics, bone quantity, and bone quality appeared to be comparable between the s-CAIS and d-CAIS groups. Also, the difference in the primary stability between the 2 groups, if any, could be attributed to the effect of the surgical techniques. As shown in Table 5 and Figure 6, the ITV of the s-CAIS group was statistically higher than that of the d-CAIS group, indicating that the osteotomy accuracy of s-CAIS was higher than that of d-CAIS. The improved accuracy may have been because of the restriction of surgical guides, which could have minimized the coronal-apical and lateral movements of the implant drills when using s-CAIS. In contrast, the intraoperative adjustment in d-CAIS may increase the accuracy of implant placement but decrease the accuracy of osteotomy by repetitive adjustment in depth and angle.
To use CAIS for implant placement, special attention should be paid to the imaging errors caused in the acquisition and analysis of CBCT images as such images are the basis of the subsequent treatment steps.
In addition, measures should be taken to control the technical errors caused in the fabrication of surgical guides in s-CAIS and in the calibration and registration steps in d-CAIS.
Additionally, human errors caused by hand movement and poor hand-eye coordination may influence the use of d-CAIS, particularly for implant surgeries in the anterior maxilla with anatomic difficulty.
Expectation and reality of guided implant surgery protocol using computer-assisted static and dynamic navigation system at present scenario: evidence-based literature review.
Even so, human errors cannot be eliminated. With the development of robots, implant placement could be completed by mechanical arms with computer guidance to avoid human errors.
Prospective investigations with more participants are indicated although the sample size of the present study was larger than the calculated value based on a previous study
and the power for ITV and Dan was greater than 0.8. Limitations of the present study included that only postoperative CBCT images were available for the determination of implant position. Information bias could have been increased by the poor quality of the CBCT images caused by metal artifacts and participant movements during scanning and also by error in matching the preoperative and postoperative CBCT images. Intraoral scanning should be used in future studies to avoid the research-related radiation exposure and provide more accurate measurements.
A method to evaluate the accuracy of dental implant placement without postoperative radiography after computer-guided implant surgery: a dental technique.
Additionally, the ITV was determined by using torque wrenches whose readings have been inaccurate. Although the implant surgeries had been completed by 2 senior surgeons, errors of ITV appeared to increase from inaccurate reading on the wrench and lack of interobserver calibration. Resonance frequency analysis should be used to evaluate the primary stability in prospective investigations in the future to reduce errors caused by observers and devices.
Based on the findings of this retrospective case-control study, the following conclusions were drawn:
1.
Comparable linear positioning accuracy and higher angular deviation were found for implants placed in the esthetic zone by using s-CAIS when compared with d-CAIS.
2.
Higher primary stability of implants may be achieved by using s-CAIS, as s-CAIS seems to have higher osteotomy accuracy than d-CAIS.
Comparison of the accuracy of implant position for two-implants supported fixed dental prosthesis using static and dynamic computer-assisted implant surgery: a randomized controlled clinical trial.
Expectation and reality of guided implant surgery protocol using computer-assisted static and dynamic navigation system at present scenario: evidence-based literature review.
Accuracy and primary stability of tapered or straight implants placed into fresh extraction socket using dynamic navigation: a randomized controlled clinical trial.
Immediate implant placement with transmucosal healing in areas of aesthetic priority. A multicentre randomized-controlled clinical trial I. Surgical outcomes.
A method to evaluate the accuracy of dental implant placement without postoperative radiography after computer-guided implant surgery: a dental technique.
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